#nav {
    ul {
        :nth-child(1),:nth-child(2),:nth-child(3){
            background: #43240c;
            color: #fff;
        }
        :nth-child(4) {
            /* 导航选中时的样式 */
            background-color: #fee44e;
            color: #43200c;
        }
    }
}